Adaptive Behavior of Triticum aestivum L. to Tolerate Salinity and Alkalinity: Growth, Physiological, and Ultrastructure Responses to Amendment with Endophyte Aspergillus terreus

Salinity and alkalinity restrict plant growth. We studied plant resistance to stress by estimating some parameters such as growth parameters and antioxidant enzymes using wheat hydroponic cultivation. The endophyte Aspergillus terreus was used to promote wheat growth in saline and alkaline conditions. Growth parameters decreased for seedlings grown under stresses while increased for seeds treated with A. terreus compared to controls. Relative water content (RWC) decreased with an increase in membrane injury (MI) level in the non-inoculated seedlings, while inoculation with A. terreus showed higher RWC and lower MI. Photosynthetic pigments decreased in non-inoculated seedlings, but significantly higher chlorophyll contents were detected in inoculated seedlings. The drop was higher in alkaline stress than in saline stress. In inoculated seedlings under stressors, catalase and peroxidase activities were more than their counterpart in uninoculated seedlings, while the level of superoxide dismutase decreased under salinity and alkalinity conditions compared to control. The levels of glutathione reductase increased in response to small stress but in case of high NaCl the level decreased drastically compared to control. Moreover, the fungal inoculated seedlings showed noticeably higher sugar and protein contents than uninoculated seedlings. The indole-3-acetic acid production considerably increased in inoculated seedlings compared to control under stress conditions. The anatomical structure of leaves using transmission electron microscopy revealed organized grana in inoculated seedlings, while in uninoculated seedlings grana and stromata lamellae were diffused. In conclusion, inoculation with fungi to wheat seedlings improves all growth parameters of the plant and could be used as a growth-promoting factor.